Hi guys,

Id like to change my gear ratio on my eagle 3 titanium. Right now it is 7.92 (95t/12t), and I would like to go to 8.25. Would it be possible to directly swap the 95T to a 99T without any modification? Or is the 99T physically larger than the 95T?

I'm thinking of changing the ratio to better match the powerband of the os 15gt that I have installed on it

No problem. The mesh is perfect.

That interesting. I owned a 03 WC E3. It used a unique diameter 12 tooth pinion which was not the same as the ones used in the Freya to support so many ratios. It's larger with teeth that precisely fit the mod 1 main gear teeth. What exact part number Hirobo 11t pinion with the same diameter as the E3 12 tooth did you use to preserve the correct gear mesh?

Ben Minor

Peak Aircraft/Team Minicopter Team Futaba Team Kontronik USA

Gears

0414-187 is the Freya generation clutch bell and pinion gear. In that series there was the stock 10 tooth and 8.3 gear ration 11T. They worked with the 95 and 93 teeth gears. 12/95 was the largest of the two gear types and the max. 12/93 and 11/93 worked just fine as did 11/95 and stock 10/95. Looks like the later pinions for the D3 and Eagle 3's changed tooth profile. They look sharper. One of the other 11t and 12t Freya pinions had a rounded tip too but I don't recall which one. I want to say the 11t. It looked weird, but we ran them and had no troubles.

Still no problems, only solutions, governed by MARSHALL AMPLIFICATION. I'm a HIROBO Fan, R U?

as I understand when changing gear ratios one must reverse the bearing holders that run along the main mast through the main gear. This is done to account for the very real physical size differences between a 95t or a 91T. For example. In the 2004 E3 the mast passes through a solid single piece of aluminum that rests between the upper and lower bearing holder therefore reversing the bearing holders would prevent the mast from aligning with that aluminum piece that cannot be adjusted at all.

Therefore are you suggesting that all the pinion gears are physically altered in such a manner that they make up for the physical dimensional differences in the main gear sizes and therefore do not require any manipulation of the position of the main mast?

The Freya changes nothing but tooth profile for its 10, 11, and 12 tooth pinions. Major pinion diameter is relatively conserved. The same applies for the maingears. The E3 12 tooth pinion is 1.5mm or so larger in major diameter as measured at the tips of its teeth than any Freya pinion. I just measured ones I had leftover. There is no OEM 11t nitro E3 pinion that shares the same major diameter as the 12 to my knowledge; Jeff can confirm. You cannot run a Freya pinion in an E3. You're stuck with whatever ratios you get with the various maingear choices and a 12t pinion.

Ben Minor

Peak Aircraft/Team Minicopter Team Futaba Team Kontronik USA

If you look at the Eagle and the TD3 the first thing you'll see is that there is only one gear ratio available. What Hirobo does is they machine the main gear and the pinion to a fixed center distance which has to happen since the main shaft and the engine shaft distances are not adjustable on the Eagle or Freya for that matter. If you want to change the gear ratio it is not a simple matter of just arbitrarily changing a pinion. In the cases where the main gears are not changed and the pinions are like on an EVO/SDX or FREYA/EVO Series then what Hirobo does is to change the pitch circle calculations on the pinion but they keep the center distance at a fixed value. When they change the number of teeth on the pinion the pitch circle is adjusted by changing the root diameters and recalculating the backlash which results in a change in size of the top land.

This process is how Hirobo jiggers the numbers from nominal gear calculations in the Metric Mod series without having the ability to adjust the center distances of the driver and the driven gears.

Hirobo's response

Thank you for your inquiry.

There is no problem using 91T main gear. For pinion gear, stock 12T
(that comes with the kit) is the only pinion gear. There is 10T/11T/12T
pinion choice to Freya Evo series, but they do not fit Eagle 3 VPUS.

So I guess i cannot go 8.25 on this heli (as 95t is the largest main gear that can fit)

I take it from Hirobo's response that would be an affirmation of what Ben and I have said then?

Thanks Terry and Dr. Ben for pitching in here.

Sorry for the late reply.

In looking at the manuals for the E3 Titanium (VPUS), which is basically a different color frame of the E3WC VPUS, and the E3 EP AOCC manuals, the main gears are all the same original part numbers. The Titanium uses a triple bearing clutch stack pinion gear block (2 10x19's and one 6x 19. Also the titanium does not have an adjustable middle main shaft bearing block, so the two with notches are not allowed to be moved. The E3 AOCC SWM does use an adjustable middle servo frame mast block allowing Eagle2 and Freya gears to be used along with a standard gear from the 1st eagle ex. The gears are the 93T 0404-706, 95T 0404-707, and 97t 0404-054.

Doing some research on the net and here, looks like the 91T was machined to fit like a 95, or 93. The first thread I came across here on RR, these were used on Freya's which have no adjustment. After and before VPUS Eagles, you could get some adjustment by turning the blocks around (also done on the Tsurugi). Looks like the smaller pinion gear teeth are made longer to fit the smaller gear like the 91.

When Hirobo went to the E3 with the longer pinion for dual BB, support parts changed. Your E3 Titanium uses that longer pinion. The longer pinion is found on the 0414-330 clutch bell as 12t, 0414-404, 11T, and 0414-403 10t.

The Freya had pinions available separately, the E3 does not it looks like. E3 pinions are sold with clutch bells. Getting separate pinion was something we asked for when I was at MRC.

The D3 V1 pinion will not work at all so the 99 and 96 main gears are all that can be used on that model.

D3 V2 uses the E3 VPUS style pinions and clutch bell.

Hope this helps. If I made any mistakes here, let me know. This is really good to know. Nice to know the main gears are the same over the years except for the D3 V1

Jeff G.

Still no problems, only solutions, governed by MARSHALL AMPLIFICATION. I'm a HIROBO Fan, R U?

Yes you are right. One might be able to use a 10/97 combo, but that is not what you are looking for. LOL. But we did find a solution.

I am going on my findings here, but it looks like the 91T gear will work with 0414-404 11T pinion clutch bell assembly which is 8.27 to one and probably the only combination close to 8.25. Then it does not matter if the main shaft bearing blocks can be moved or not. The Freya plastic does not and accommodates the 12/95 nicely. It's a tight fit, but it works nice. It breaks in and that is what you have now.

Whew, that's a lot. LOL No where is this info available at HIROBO. Guess I will post on HUFS and send to them unless they already have the info and I missed it. Probably the case. LOL

Still no problems, only solutions, governed by MARSHALL AMPLIFICATION. I'm a HIROBO Fan, R U?

Lower head speed more efficient.

E3 AOCC/SWM/VPUS nitro models all share the 0414-314 fixed bearing spacing, one piece, machined ali "spine" that fixes the distance between the main mast and the clutch stack. It's clear on the plans. It will only support the 12t E3 pinion and the various fixed major diameter main gears (93,95, etc). No other pinion in the Hirobo line will work in a nitro E3.

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